The Pet Food Institute says the manufacturers comply with current laws and keep an eye on standards set by other agencies.

“As we learn more about the nutrition requirements of cats and dogs, and as new ingredients evolve, the profiles are revised," says Ekedahl.

But vets say the terms might be more about marketing. We found no definition for “natural” but there are industry guidelines set up for pet food companies to follow. There should not be artificial colors, flavors or preservatives.

“You can still be using by-products; you can still be using all sorts of things that might not be the best quality, but they’re still natural, so you can put natural on your pet food label,” says Dr. Nelson.

Look for claims that say “complete” and “balanced”. That’s actually defined by law, and a company must prove its food contains all the nutrients necessary for a healthy dog or cat.

So why would pet food makers put all those terms on products? The Pet Food Institute says pet owners will know the difference.

“They know the coats, they know the energy levels they, they know how much the cat or dog likes the foods,” says Ekedahl.

Meantime, down owner Ilana says doing all the research to find the best pet food was confusing at times, but worth it.

"My dog is very happy and healthy now that he is on the right food," says Ilana.

The USDA says it's working to come up with rules and regulations to define exactly what is "organic" pet food.